Materials with supramolecular chirality : liqid crystals and polymers for catalysis

Abstract

Mesomorphic organizations provide a powerful and efficient method for the preorganization of molecules to create synthetic materials with controlled supramolecular architectures. Incorporation of polymerizable groups within a liquid crystalline template can set the stage for the synthesis of anisotropic molecular networks. This dissertation details the synthesis and characterization of chiral liquid crystals and crosslinked polymer networks, with an eye toward applications in asymmetric catalysis. Chapter One gives an introduction to the study of liquid crystals and their phases. Chapters Two and Three describe the incorporation of terminal olefins as polymerizable groups within a columnar liquid crystalline template as an effective method for the synthesis of robust, anisotropic polymeric materials. Upon in situ acyclic diene metathesis (ADMET) polymerization, the original mesophase order is retained. Chapter Two involves the room temperature polymerization of iron(III) tris(diketonate) liquid crystals, resulting in densely crosslinked materials. The focus of Chapter Three is the polymerization of dioxomolydenum-based liquid crystals, performed at high temperature, and their potential to serve as catalysts for asymmetric epoxidation. In Chapter Four, a different approach towards the synthesis of catalytically active anisotropic materials is taken, incorporating well-established, transition metal catalysts within a liquid crystalline framework. Progress towards the formation of liquid crystal phases containing C₂- symmetric bis(oxazoline) and pincer ligands is detailed. Finally, Chapter Five describes the immobilization of chiral monodentate oxazoline ligands for use as catalysts in asymmetric cyclopropanation. Preliminary results indicate that the heterogeneous system gives higher enantioselectivities than the analogous homogeneous system.